In North Carolina, the storm surge from Isabel washed out a portion of Hatteras Island to form what was unofficially known as Isabel Inlet. Damage was greatest along the Outer Banks, where thousands of homes were damaged or even destroyed. The worst of the effects of Isabel occurred in Virginia, especially in the Hampton Roads area and along the shores of rivers as far west and north as Richmond and Washington, DC. Virginia reported the most deaths and damage from the hurricane. About 64% of the damage and 69% of the deaths occurred in North Carolina and Virginia. Electric service was disrupted in areas of Virginia for several days, some more rural areas were without electricity for weeks, and local flooding caused thousands of dollars in damage.

Moderate to severe damage extended up the Atlantic coastline and as far inland as West Virginia. Roughly six million people were left without electric service in the eastern United States from the strong winds of Isabel. Rainfall from the storm extended from South Carolina to Maine, and westward to Michigan. Throughout the path of Isabel, damage totalled about $5.5 billion (2003 USD). 16 deaths in seven U.S. states were directly related to the hurricane, with 35 deaths in six states and one Canadian province indirectly related to the hurricane.

A tropical wave moved off the western coast of Africa on September 1.[1] An area of low pressure associated with the wave moved slowly westward, and its convection initially appeared to become better organized.[2] On September 3, as it passed to the south of the Cape Verde islands, organization within the system degraded,[3] though convection increased the next day.[4] The system gradually became better organized, and Dvorak classifications began early on September 5. Based on the development of a closed surface circulation, it is estimated the system developed into Tropical Depression Thirteen early on September 6. Hours later, it intensified into Tropical Storm Isabel,[1] though operationally the National Hurricane Center did not begin issuing advisories until 13 hours after it first developed.[5]

Located within an area of light wind shear and warm waters, Isabel gradually organized as curved bands developed around a circular area of deep convection near the center.[6] It steadily strengthened as it moved to the west-northwest, and Isabel strengthened to a hurricane on September 7 subsequent to the development of a large, yet ragged eye located near the deepest convection.[7] The eye, overall convective pattern, and outflow steadily improved in organization,[8] and deep convection quickly surrounded the 40-mile (60 km)-wide eye.[9] Isabel intensified on September 8 to reach major hurricane status while located 1,300 miles (2,100 km) east-northeast of Barbuda. On September 9, Isabel reached an initial peak intensity of 135 mph (215 km/h) for around 24 hours, a minimal Category 4 hurricane on the Saffir–Simpson Hurricane Scale.[1]

Early on September 10, the eyewall became less defined, the convection near the eye became eroded, and northeasterly outflow became slightly restricted.[10] As a result, Isabel weakened slightly to a Category 3 hurricane. The hurricane turned more to the west due to the influence of the Bermuda-Azores High.[1] Later on September 10, Isabel restrengthened to a Category 4 hurricane after convection deepened near the increasingly organizing eyewall.[11] The hurricane continued to intensify, and Isabel reached its peak intensity of 165 mph (270 km/h) on September 11, a Category 5 hurricane on the Saffir–Simpson Hurricane Scale.[1] Due to an eyewall replacement cycle, Isabel weakened slightly, though it retained Category 5 status for 24 hours.[12] As Isabel underwent another eyewall replacement cycle, outflow degraded in appearance and convection around the eye weakened,[13] and early on September 13, Isabel weakened to a strong Category 4 hurricane. A weakness in the ridge to its north allowed the hurricane to turn to the west-northwest.[1] After completing the replacement cycle, the hurricane's large 40 mile (65 km) wide eye became better defined,[14] and late on September 13, Isabel re-attained Category 5 status.[1] During this time, Isabel attained annular characteristics, becoming highly symmetrical in shape and sporting a wide eye.[1] A NOAA Hurricane Hunter Reconnaissance Aircraft flying into the hurricane launched a dropsonde which measured an instantaneous wind speed of 233 mph (375 km/h), the strongest instantaneous wind speed recorded in an Atlantic hurricane.[15] Cloud tops warmed again shortly thereafter,[16] and Isabel weakened to a strong Category 4 hurricane early on September 14. Later that day, it re-organized, and for the third time, Isabel attained Category 5 status while located 400 miles (650 km) north of San Juan, Puerto Rico.[1]

Cloud tops around the center warmed again early on September 15, and Isabel weakened to a Category 4 hurricane.[1] Later that day, the inner core of deep convection began to deteriorate, while the eye decayed in appearance. As a ridge to its northwest build southeastward, it resulted in Isabel decelerating as it turned to the north-northwest.[17] Increasing vertical wind shear contributed in weakening the hurricane further, and Isabel weakened to a Category 2 hurricane on September 16, while located 645 miles (1035 km) southeast of Cape Hatteras, North Carolina.[1] Convection remained minimal, though outflow retained excellent organization,[18] and Isabel remained a Category 2 hurricane for two days, until it made landfall between Cape Lookout and Ocracoke Island on September 18, with winds of 105 mph (165 km/h). The system weakened after it made landfall, though due to its fast forward motion, Isabel remained a hurricane until it reached western Virginia, early on September 19. After passing through West Virginia as a tropical storm, Isabel became extratropical over Western Pennsylvania, near Pittsburgh. The system continued turned northward, and crossed Lake Erie into Canada. Early on September 20, the extratropial remnant of Isabel was absorbed by a larger extratropical storm, over the Cochrane District of Ontario.[1]

Officials declared mandatory evacuations for 24 counties in North Carolina, Virginia, and Maryland, though in general not many left. According to a survey conducted by the United States Department of Commerce, evacuation rates were estimated as follows; 45% in the Outer Banks, 23% in the area around the Pamlico Sound, 23% in Virginia, and about 15% in Maryland.[19] The threat of Isabel resulted in the evacuation of hundreds of thousands of residents, primarily in North Carolina and Virginia, and included more than 12,000 residents staying in emergency shelters.[20]

19 major airports along the East Coast of the United States were closed, with more than 1,500 flights canceled. The Washington Metro and Metrobus system closed prior to the arrival of the storm, and Amtrak canceled nearly all trains south of the nation's capital. Schools and businesses throughout its path closed prior to Isabel's arrival to allow time to prepare; hardware and home improvement stores reported brisk business of plywood, flashlights, batteries, and portable generators, as residents prepared for the storm's potential impact. The federal government was closed excluding emergency staff members.[20] The United States Navy ordered the removal of 40 ships and submarines and dozens of aircraft from naval sites near Norfolk, Virginia.[21]

A contingency plan was established at the Tomb of the Unknowns at Arlington National Cemetery that, should the winds exceed 120MPH, the guards could take positions in the trophy room (above the Tomb Plaza and providing continual sight of the Tomb) but the plan was never implemented. However, it spawned an urban legend that the Third Infantry sent orders to seek shelter, orders that were deliberately disobeyed.[22]

Strong winds from Isabel extended from North Carolina to New England and westward to West Virginia. The winds, combined with previous rainfall which moistened the soil, downed many trees and power lines across its path, leaving about 6 million electricity customers without power at some point. Parts of coastal Virginia, especially in the Hampton Roads and Northeast North Carolina areas, were without electricity for almost a month. Coastal areas suffered from waves and its powerful storm surge, with areas in eastern North Carolina and southeast Virginia reporting severe damage from both winds and the storm surge. Throughout its path, Isabel resulted in $5.5 billion in damage (2003 USD) and 51 deaths, of which 16 were directly related to the storm's effects.[28][29]

Powerful surf affected the northern coastlines of the islands in the Greater Antilles. Strong swells also lashed the Bahamas. During most hurricanes, the location of the Bahamas prevents powerful swells of Atlantic hurricanes from striking southeast Florida. However, the combination of the location, forward speed, and strength of Isabel produced strong swells through the Providence Channel onto a narrow 10 mile (16 km) stretch of the southeastern Florida coastline; wave heights peaked at 14 feet (4.3 m) at Delray Beach.[15] The swells capsized a watercraft and injured its two passengers at Boynton Beach, and a swimmer required assistance to be rescued near Juno Beach. Minor beach erosion was reported in Palm Beach County.[31] In the northern portion of the state, waves reached up to 15 feet (4.5 m) in height at Flagler Beach, causing the Flagler Beach Pier to be closed due to damaged boards from the waves.[32] Rip currents from Isabel killed a surfer at an unguarded beach in Nassau County, with an additional six people requiring rescue from the currents.[33] The beaches were later closed during the worst of the rough surf.[34]

Isabel produced moderate to heavy damage across eastern North Carolina, totaling $450 million (2003 USD).[1] Damage was heaviest in Dare County, where storm surge flooding and strong winds damaged thousands of houses.[36] The storm surge produced a 2,000 foot (600 m) wide inlet on Hatteras Island, unofficially known as Isabel Inlet, isolating Hatteras by road for two months.[37] Strong winds downed hundreds of trees of across the state, leaving up to 700,000 residents without power. Most areas with power outages had power restored within a few days.[36] The hurricane directly killed one person and indirectly killed two in the state.[38]